Human face has a large number of muscles that move and cause facial changes in result of feelings and intentional movements of the jaw, nose, and lips, for instance. Human beings largely rely on such non-verbal information that we see of one another in our natural intercourse. Machines, however, are not typically capable of making use of non-verbal information. So far, motion of facial muscles has been detected by electrodes attached to the cheek of a person and by processing image information of a camera that is focused on the face of the person.